서울대병원 / 박효준, 김정인*
Abstract
The leaf width of a multileaf collimator (MLC) determines the dose conformity to the target volume. The objective of this study was to investigate the feasibility of a two-dimensional dynamic MLC (2DDMLC) to improve the treatment plan quality with a fixed leaf width. The treatment head of the Clinac™ linear accelerator with the Millennium 120™ MLC was modelled with the Geant4 (for GEometry ANd Tracking) tollkit using the Monte Carlo (MC) method. The 2DDMLC produces a beam aperture by moving the MLC bank vertically to the leaf movement. Thus, the effect of the 2DDMLC motion on beam divergence and beam fluence resolution was evaluated by comparing the dose distributions between the conventional MLC motion and the 2DDMLC. Finally, the 2DDMLC was employed for dynamic conformal arc therapy for 13 brain cancer patients. The dose-volumetric parameters, including the dose delivered to 98% of the target volume (D 98%), percent volume given 20% of the prescribed dose (V 20%), and conformity index (CI) were compared with those of the conventional MLC. For the 6 MV beam of the MC model, the depth dose and lateral dose distribution differed by less than 2% between the simulation and measurement. The 2DDMLC did not significantly influence beam divergence and sharpened the beam. In clinical use, the dose delivered to the target was almost identical between the 2DDMLC and conventional MLC (D 98% = 29.74 Gy versus 29.71 Gy, p = 0.18). The CI was improved with the use of the 2DDMLC (CI = 1.49 versus 1.47, p = 0.14). Moreover, irradiation of normal tissue was reduced with the 2DDMLC compared with conventional MLC (V 20% = 17.22% versus 17.45%, p < 0.001). The 2DDMLC improved the dose conformity to the target volume and reduced the irradiation of the normal tissue compared with the conventional MLC.
Author information
Park H1, Choi HJ, Hee Min C, Kim JI.
1
Department of Radiation Convergence Engineering, Yonsei University, Wonju, Republic of Korea.
편집위원
방사선치료의 비약적인 발전은 90년대 MLC의 발전으로 촉발되었다고 해도 과언이 아닐 것인데, 최근 mlc를 이용한 트래킹 기법이나, 이중적층 mlc(?)등의 새로운 디자인이 상용화되어 발전을 이어가고 있다. 이 논문 또한 mlc를 y방향으로 움직여 mlc폭을 줄이는 효과를 보고자 한 것으로 MC 시뮬레이션으로 그 결과를 예측하였다. 향후 mlc가 더욱 발전하여 보다 정밀한 방사선치료료 암환자의 방사선치료 부작용이 더 줄어들 수 있었으면 하는 바램이다.
2020-01-30 17:32:20